This invention pertains to a catheter patency flush flow controller and particularly to a push-button type flush flow controller wherein, during both the slow flow and fast flush mode, the internal space of the controller is positively sealed against both inward and outward leakage.
An in-dwelling vascular catheter may be used for clinical monitoring of blood system pressure at a particular point in the vascular network and for the study of related parameters including arterial pulse wave form, stroke volume, heart rate, cardiac output, duration of systole, and systolic, diastolic, and mean blood pressure. For pressure monitoring through the catheter, the catheter must be kept filled with liquid and free of contaminants and gas bubbles. In addition, the tendency of blood to clot at the tip of the catheter must be prevented, typically by maintaining a very slight positive pressure of a saline fluid which fills the catheter and flows through the catheter, through its tip and into the blood stream at a very slow and well controlled rate, on the order of 2-4 milliliters per hour. From time to time, the catheter must be flushed, with a high rate flow, on the order of 150-400 milliliters per minute, of saline fluid, in order to eliminate gas bubbles, flush contaminants and otherwise maintain the patency of the catheter and the continuity of the fluid contained therein.
A variety of apparatus has been devised for this purpose, gradually evolving through a system including multiple path and stopcock connections between a saline fluid source and the catheter (as in U.S. Pat. No. 3,581,733--Grandjean). Subsequently, a number of catheter patency flow-flush controllers have been devised with a fail-safe valve, for the flush mode, either in a bypass passageway, as in U.S. Pat. No. 3,675,891--Reynolds et al, or with various types of push-button valve actuations, with the valve spring loaded in the flush path closed position, as seen for example in U.S. Pat. No. 4,200,119--Cunningham, U.S. Pat. No. 4,210,178--Morse et al, and U.S. Pat. No. 4,291,702--Cole et al. Still another fail-safe multiple passageway configuration is seen in U.S. Pat. No. 4,192,303--Young et al.
A further patent cited in the prosecution of U.S. Pat. No. 3,675,891 is U.S. Pat. No. 1,983,227--Hall et al. The Hall et al patent discloses a gas pilot light control including a high rate flow path for pilot lighting and a low rate continuous flow path for normal pilot light maintenance, in which a push-button valve is utilized to open the fast flush path. The push-button valve shown in the Hall et al patent is somewhat similar to that utilized in the present invention.
Still another push-button design is embodied in a catheter patency flow-flush controller sold by the American Medical Products Corporation. In this controller, the push-button valve actuator comprises a plunger with an enlarged cross section valve closing portion, biased upwardly against a valve seat in the internal passageway of the device, by a coil spring disposed within the valve housing and at the end of the valve plunger. The slow flow capillary passageway extends through the center of this valve plunger in the American Medical Products device. Leakage into and out of the internal passageway of the controller in the American Medical Products device is prevented by an O-ring surrounding the valve plunger at its entry into the valve housing. (A cross-sectional sketch of this device is submitted, for purposes of examination, with this application but should not otherwise be considered part of the application.)
Notwithstanding these prior developments in the field of catheter patency flush flow controllers, there remains a continuing need for, and it is the general object of this invention to provide, controllers improved in one or more, and preferably all, of the following respects: positive leak prevention in all operational modes; simplified internal configuration to minimize formation of gas bubbles; fail-safe valve design, which facilitates proper finger actuation with one hand and a minimum of visual observation, which minimizes the possibility of inadvertent actuation and which precludes valve malfunction through valve misalignment or disassembly.
It is also an object to provide a catheter patency flow-flush controller with these improved functional features, which is also improved with respect to ease of manufacture and is safer due to reduced likelihood of manufacturing and assembly defects.